Effectiveness of Real-Time Query Expansion in a Library Catalog

摘要

Query expansion (QE) is a potentially effective technique tohelp searchers formulate or improve their search. In January2010, the University of North Carolina at Chapel Hill(UNC) Library made an effort to improve user interactionswith authority data in its online catalog. It introduced a realtimequery expansion feature for the catalog interface thatwould provide real-time suggestions based on what the userhad typed in the search box. QE is not a new technique, andhas been widely used in web search interfaces. It has rarelybeen adopted by library catalogs though. From the librariesperspective, populating the query expansion feature withauthority data provides a balance between traditional libraryuse of authority records and the expectations users havefrom their use of Web search engines. By analyzing thesearch logs from the library server, we investigate theimpact of this feature on users’ search behavior. Twosampling periods of logs were chosen: April 2009 (beforethe feature’s launch) and April 2010 (after the feature’slaunch). Totally, we have analyzed approximately 200Mlog data with approximately 800,000 useful log records.Results showed that users take the suggestions 20.26% ofall searches. There was a significant increase in the rate ofsubject searches. The library catalog interface supportingdynamic query expansion also leads to longer queries, lessquery iterations per search, and fewer result items viewedper search. In addition, search failure rate has seen a greatdrop. However, results also imply some issues may existwith the use of query expansion, necessitating properhandling of the search expansion interface. Our findingshave implications for how query expansions should beoffered to library catalogs to increase the use of library’scollection.